This invention relates to a helical scanning type of magnetic recording/reproducing apparatus having a mechanism for running a magnetic tape.
Conventionally, a following mechanism for running a magnetic tape is provided in a recording/reproducing apparatus such as a video tape recorder (hereinafter referred to as "VTR"), which performs helical scanning over a surface of a magnetic tape with rotary magnetic heads and records and reproduces signals thereon. The mechanism is constructed on a main chassis or a base for supporting the appratus. This mechanism has the following components disposed over the main chassis: magnetic heads; a cylindrical rotary drum which has magnetic heads mounted in an outer periphery thereof and which has an axis of rotation inclined relative to a horizontal major surface of the main chassis at an angle equal to the lead angle (the inclination of the plane of rotation of the magnetic heads relative to a direction in which a magnetic tape travels); a stationary drum which is disposed below the rotary drum coaxially therewith and has a lead portion formed on an outer periphery thereof for guiding the magnetic tape; means for driving and rotating the rotary drum; a cassette which accommodates the magnetic tape wound around reels; and an entrance-side tape position regulation guide which draws the magnetic tape out of the cassette to obliquely wind it around the outer peripheries of the rotary and the stationary drums. This entrance-side tape position regulation guide keeps the position of the magnetic tape higher than the center of the plane of rotation of the magnetic heads in a section where the magnetic tape starts to wind upon the drums (tape entrance section), thus controlling the position of the magnetic tape under the tape wound condition. The mechanism further has the following components disposed over the main chassis: an exit-side tape position regulation guide for keeping the position of the magnetic tape lower than the center of the plane of rotation of the magnetic heads in a section where the magnetic tape starts to unwind from the drums (tape exit section) and at the same level as a reference plane (hereinafter referred to as "central reference plane") corresponding to the widthwise center of the magnetic tape in the cassette in order that the recording surface of the magnetic tape is perpendicular to the central reference plane and, at the same time, the tape travel direction is parallel to the central reference plane; and a loading ring to which the entrance-side tape position regulation guide and the exit-side tape position regulation guide are connected, and which ring has an annular structure encircling the rotary and the stationary drums, and which ring is disposed parallel to the major surface of the main chassis. Under the main chassis are disposed a capstan motor for running the magnetic tape and a flywheel for increasing the inertia of the capstan motor, both of which are so disposed as to avoid interfering with the loading ring.
An example of this conventional arrangement is disclosed in JP-A-57-86161.
The above-described conventional art entails the following problems.
1) The loading ring is disposed parallel to the major surface of the main chassis. The magnetic tape is so retained and controlled relative to the rotary and stationary drums by the exit-side tape position regulation guide that the magnetic tape is maintained at the tape exit section at the same level as the central reference plane and in perpendicular to the central reference plane and the tape travel direction is parallel thereto. Accordingly, the direction and the angle of inclination of the rotary and the stationary drums must be limited within certain ranges to maintain desired magnetic tape running performance. It is also necessary to place the center of the plane of rotation of the magnetic heads substantially higher than the central reference plane. Accordingly, the magnetic tape starts to wind the rotary and the stationary drums at a higher position in the tape entrance section. Correspondingly, the entrance-side tape position regulation guide occupies a higher position in that section, so that a top end of the entrance-side tape position regulation guide projects upwards far beyond an upper end of the rotary drum. The top end of the rotary drum is placed much higher than the central reference plane to a large extent and also higher than an upper end of a cassette front lid which defines the upper end of the cassette. In consequence, the distance in the vertical direction between the central reference plane and the top end of the entrance-side tape position regulation guide is so large that the overall thickness of the mechanism is considerably increased. PA0 2) The capstan motor and the flywheel both attached to a reverse side of the main chassis are the thickest ones of the component parts disposed under the main chassis, and the lower ends of the capstan and the flywheel project downward to largest extends. Therefore, the thickness of the section below the main chassis is considerably increased. An electronic circuit board is also disposed on the reverse side of the main chassis. It is necessary to form cutout portions in this circuit board for providing spaces for attachment of the capstan motor and the flywheel. Therefore the configuration of the electronic circuit board becomes complicated, and the area required for wiring is restricted. In addition since the capstan motor and the flywheel are disposed under the main chassis, the assembly of these components into the main chassis is difficult.